Question: Simplify the following expression: $x = \dfrac{r}{2} - \dfrac{8r}{5}$
Explanation: In order to subtract expressions, they must have a common denominator. The smallest common denominator is the least common multiple of $2$ and $5$ $\lcm(2, 5) = 10$ $ x = \dfrac{5}{5} \cdot \dfrac{r}{2} - \dfrac{2}{2} \cdot \dfrac{8r}{5} $ $x = \dfrac{5r}{10} - \dfrac{16r}{10}$ $x = \dfrac{5r -16r}{10}$ $x = \dfrac{-11r}{10}$